The biological characteristics of the C-1300 murine neuroblastoma will be defined and an in vivo model developed to study the mechanisms of action of drugs that influence tumor viability and differentiation. Specific aims of this proposal will be to clarify the regulatory role of macromolecular methyltransferases on cyclic nucleotide metabolism, establish longitudinal correlates between catecholamine metabolism and biosynthesis and tumor growth in vivo and to quantitate the effects and mechanisms of pharmocologic agents that modify methyltransferase activity or alter adrenergic neuronal function. The investigation will test the hypothesis that macromolecluar methylation systems function as molecular regulators of neuroblastoma growth and tumor differentiation.